As is well known, ordinary silver halide multilayered color photographic light-sensitive materials are obtained by coating a red-sensitive silver halide emulsion layer containing a cyan dye-forming coupler, a green-sensitive silver halide emulsion layer containing a magenta dye-forming coupler, and a blue-sensitive silver halide emulsion layer containing a yellow dye-forming coupler one on the other on a support.
Usually, the red-sensitive layer responds to the light of 600 to 700 nm in wavelength, the green-sensitive layer to the light of 500 to 600 nm, and the blue-sensitive layer to the light of 400 to 500 nm. However, these color sensitivities are not definite in the respective wavelength regions, but each layer has a particular spectral wavelength distribution depending upon the kinds of spectrally sensitizing agents and other materials used. Thus, the peak position and the overlap in spectral sensitization distribution differ depending upon the selection and the combination of the sensitizers and other materials. This is one great factor which governs color reproducibility of a color light-sensitive material.
In view of recent technical progress of silver halide multilayered color photographic light-sensitive materials, good color reproduction can be obtained as long as exposure conditions upon photographing and subsequent processings, printing, and projecting conditions are appropriate. However, if these conditions or procedures are inappropriate, satisfactory color reproduction is not always obtained. The interests of those skilled in the art have conventionally been directed to the solution of this problem by improving color photographic light-sensitive materials. Exposure conditions upon photographing include exposure amount, exposure time, light amount distribution of photographed object (lighting conditions), color temperature of light source, and the like. For example, as to improvement of color reproduction of a particular blue color, Japanese Patent Application (OPI) No. 20926/78 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") describes the technique of shifting the spectral sensitivity wavelength of a less sensitive layer of red-sensitive layers to the shorter wavelength side and, as to dependency on the color temperature of a light source, Japanese Patent Publication No. 6207/74 describes that good color reproduction can be obtained for exposure using various light sources by bringing the form of the spectral sensitivity distribution of each silver halide light-sensitive layer into harmony with a certain target curve through selection of a spectral sensitizer and a filter dye.
In these techniques, overlap between spectral sensitivity distribution of the red-sensitive layer and that of the green-sensitive layer is made larger, which concurrently causes color mixing (color stain) due to poor color separation, resulting in reduction of saturation. Poor color separation can be prevented by selecting a spectral sensitizer which possesses a sharply ending spectral absorption spectrum. However, actually existing spectral sensitizers possess a limited sharpness, with sharpness on the shorter wavelength end being particularly difficult to attain. The shorter wavelength end can be sharply cut to some extent by using a filter layer as described in Japanese Patent Publication No. 6207/74 which, however, concurrently influences spectral sensitivity distribution or reduces sensitivity of other layer possessing light absorption in the region corresponding to the absorption wavelength region of the filter.
In general, in order to reduce change in color reproducibility caused by change in color temperature of a light source upon photographing, particularly a gentle change in color temperature over the entire visible region, it is effective to shift the main region of the spectral sensitivity distribution of blue-sensitive layer to the longer wavelength side, and that of red-sensitive layer to the shorter wavelength side, i.e., to narrow the mutual gaps between the blue-sensitive layer, green-sensitive layer, and red-sensitive layer in spectral sensitivity distribution. This, however, is liable to cause deterioration of color separation as described above, leading to reproduction of color with less saturation. On the other hand, when the gaps in spectral sensitivity distribution between the blue-sensitive layer, green-sensitive layer and red-sensitive layer are broadened, color separation is not deteriorated and, therefore, saturation is not reduced. However, change in color reproducibility to be caused by change in color temperature of a light source becomes so much that good color reproducibility can be obtained only by using a specific light source and, in an extreme case, colors with subtle color difference are reproduced as one and the same color.
Color photographic light-sensitive materials are expected to reproduce various colors just as they are viewed by the eye. Colors that people recognize through the visual organ are influenced by the absorption or emission spectral distribution of an object and by the color temperature of a light source which lights the object. The difference of the color temperature of light source is recognized only as a comparatively small difference for the eye, whereas it is detected as a larger difference by color photographic light-sensitive materials. One reason for this is that relative sensitivities of three spectral sense organs of human visual sensation change depending upon the color temperature and brightness of a light source, and another reason is that spectral sensitivity distributions of the three sense organs are different from that of color photographic light-sensitive materials. The difference in spectral sensitivity distribution between the sense organs and the color photographic light-sensitive materials causes such phenomenon as that, while a color reproduced by a color photographic light-sensitive material is recognized as the same color as is directly viewed by the eye, another color is recognized as an absolutely different color.
Spectral sensitivities of the human eye have peaks at about 445 nm, 540 nm, and 605 nm, respectively, for the three sense organs. Most of the present commercially available color photographic materials, for example, color negative films, are known to have a peak of a blue-sensitive layer at a wavelength shorter than 445 nm, a peak of a green-sensitive layer at a wavelength somewhat longer than 540 nm, and a peak of a red-sensitive layer at a wavelength considerably longer than 605 nm. This means that when photographing is conducted under tungsten light which has such spectral distribution in the visible region that the longer wavelength component is relatively longer than shorter wavelength component in comparison with day light using a color negative film whose color balance is adjusted for day light. Accordingly, images with orange tint more intense than is viewed by the eye are reproduced. This can be avoided by shifting the spectral sensitivity of the red-sensitive layer to a shorter wavelength side. However, as has been described hereinbefore, such shift increases the overlap between the spectral sensitivity regions of the layers and deteriorates color reproducibility due to poor color separation.
It is abstractly known to use DIR couplers for the improvement of color reproduction. However, conventionally known DIR couplers are not fully satisfactory with respect to the effect of improving color reproduction and are absolutely powerless in avoiding deterioration of color reproduction when increasing the overlap between the spectral sensitivity distributions as described above.